In recent years, navigation-assisted operation systems have been very successfully developed in order to effectively assist the surgeon in his work. These navigation-assisted operation systems allow the treatment apparatuses used during an operation to be positioned exactly (navigated treatment apparatuses). This has enabled the risk to a patient associated with an operation to be significantly reduced. The quality of treatment outcomes has also significantly increased, and it has been possible to significantly improve the quality of life for patients after an operation.
In the known navigation systems, markers such as active signal emitters or reflectors are attached to treatment apparatuses, for example to surgical instruments. Markers (for example, active signal emitters or reflectors) are also attached to the patient. If a camera apparatus which is capable of detecting spatial position values is then used to monitor the operation area, and the markers (active signal emitters or reflectors) on the patient and the treatment apparatus are detected simultaneously, then their positions with respect to each other and therefore in turn the position of the treatment apparatus on the patient can be optimally controlled.
Navigation-assisted operation systems are also used in particular in operations in the course of which the patient has a prosthesis inserted. For instance, knee joint operations and hip joint operations using a prosthesis are now performed routinely.
By contrast, the same degree of routine use has not yet been reached in the case of shoulder operations. This is due among other things to the fact that a particularly large number of nerves and vessels are situated in the region of the shoulder, which could be injured during a navigated operation by the attachment of reference units necessary in this case for detecting the location of the shoulder or upper arm relative to the treatment apparatus, which could result in a restriction of the patient's mobility in the region of the shoulder and arm after the operation. The humerus of the shoulder joint is also a substantially smaller bone than the upper and lower leg, which can only withstand weaker stresses.
When, in a shoulder operation, the humeral component is replaced with a prosthesis, a non-navigation-assisted operation method is routinely employed in most cases. Once a way of accessing the humeral head has been operatively acquired and the humeral head has been luxated, a pilot hole is drilled into the upper region of the humerus, and the humeral canal is reamed. A cutting guide is then fastened to and orientated on a rod which is attached in the reamed canal, in order to cut off the humeral head in a defined way. Lastly, the humeral canal is prepared for implanting a prosthesis (for example by being countersunk, etc.).
A navigated system and method for shoulder operations is known from WO 2006/050010 A2. In accordance with this method, positioning reflectors and markers which are part of a tracking unit are fixedly screwed to the shoulder blade. These screws are removed again after the operation. However, it must be considered that each screwing process ultimately injured a bone. There is also the danger of a bone becoming unstable and breaking. There is also the danger of infections due to additional incisions for attaching reference units. Drilling into bones is therefore to be avoided if possible.
Attaching a fastening unit to the humerus, to which a navigation unit and/or tracking unit can be attached in different positions, is also known in shoulder operations. In this way, it is possible to attach a single tracking unit in such a way that it is particularly clearly visible to a camera system used for navigation purposes.
It is the object of the present invention to provide an improved system which is suitable for navigation-assisted shoulder operations in which the humeral component is partially replaced with a prosthesis, and in which the risks to the patient described above are simultaneously reduced. In particular, the system in accordance with the invention enables other treatment steps, which have to be performed exactly, to be performed with navigational assistance and therefore positionally more precisely.
It is also the object of the present invention to provide an improved navigation method for positioning navigated treatment apparatuses with respect to a bone.
These objects are solved by a system for navigation-assisted shoulder operations in which the humeral component is partially replaced with a prosthesis, comprising: a first tracking unit which is configured to be fastened to a section of a bone which is to be removed during the operation; a detection unit which is configured to detect landmarks on the bone; a second tracking unit which is configured to be attached to another section of the same bone; a camera unit which simultaneously detects the first and second tracking unit, in order to determine their respective location; and a computational unit which is connected to the camera unit and is configured to: determine a first relative location of the landmarks relative to the first tracking unit from data acquired by means of the detection unit; and calculate a second relative location of the landmarks relative to the second tracking unit on the basis of the first relative location; such that additional navigated treatment apparatuses can be exactly positioned during the operation by referring to the second tracking unit; and by a navigation method for positioning navigated treatment apparatuses with respect to a bone, comprising the following steps: detecting landmarks on a bone; ascertaining a first relative location of the detected landmarks relative to a first reference frame comprising at least two reference points; simultaneously detecting the at least two reference points of the first reference frame and at least two reference points of a second reference frame by means of a camera unit; calculating a second relative location of the landmarks relative to the second reference frame on the basis of the first relative location; such that the treatment apparatuses to be navigated can be exactly positioned by referring to the second reference frame. The sub-claims define preferred embodiments of the invention.